The hunt for dark matter - the mysterious and invisible substance thought to
account for a quarter of the mass of the Universe - may be over, claim
scientists.

An international team of physicists believe they may have detected two particles of the elusive substance for the first time at the bottom of a mine shaft.

Should the findings be confirmed it will have an Earth-shattering effect on our understanding of the make up of the cosmos. It will also prove once and for all the existence of the substance first hypothesised 80 years ago.

Scientists working on the Cryogenic Dark Matter Search (CDMS), in a disused iron ore mine in Minnesota, have announced that they had detected two weakly-interacting massive particles (WIMPs), that are thought to make up dark matter.

If they are confirmed by further observations that will begin next year, they would rank as one of the most important recent advances in physics and understanding of the cosmos.

Dark matter, along with the equally elusive dark energy, is believed to make up 90 per cent of the mass of the Universe. We cannot see it but scientists think it is there due to the gravitational force it exerts.

It could help account for the 'missing mass' in the Universe that would explain why galaxies stay together and rotate at their current speeds.

The particles showed as two tiny pulses of heat deposited over the course of two years in chunks of germanium and silicon that had been cooled to a temperature near absolute zero.

The detectors are place half a mile down to avoid them being effected by background radiation.

But the scientists still said there was more than a 20 percent chance that the pulses were caused by fluctuations in the background radioactivity of their cavern, so the results were tantalizing, but not definitive.

Dan Bauer, head of CDMS, said they have spotted two particles with all the expected characteristics of dark matter.

Theorist Craig Hogan from the University of Chicago said the finds are 'potentially very exciting.

He said three or four more WIMP-like interactions recorded over the next few years by the experiment, would constitute proof of dark matter.

"That would be a huge transformation in how we do science," Dr Hogan said.

"We would have a new form of matter to study."

The detectors are being upgraded with three times as much germanium making detections more likely.

Gordon Kane, a physicist from the University of Michigan, called the results “inconclusive, sadly,” adding, “It seems likely it is dark matter detection, but no proof.”

Dr Kane said results from bigger and more sensitive experiments would be available in a couple of months.

Confirmation of the particles would also constitute the first evidence for a new feature of nature, called supersymmetry, that physicists have been seeking as avidly as the astronomers have been seeking dark matter. Supersymmetry argues that every particle in the universe is paired with a twin somewhere else.

It is central to theoretical efforts like string theory, which unify all of the forces of nature into one mathematical expression.

Scientists have debated the existence of dark matter ever since a Swiss astronomer Fritz Zwicky argued that a distant cluster of galaxies would fall apart were it not for the gravitational pull of some vast but invisible cosmic substance.